Safety hook



Feb. 3, 1970 1 I A. w. SMITH 3,493,260

SAFETY HOOK Filed June 14, 1968 United States Patent 3,493,260 SAFETY HOOK Arthur W. Smith, Trenton, N.J., assignor to Eastern Rotorcraft Corporation, Doylestown, Pa., a corporation of Pennsylvania Filed June 14, 1968, Ser. No. 737,211 Int. Cl. B64d 17/38 US. Cl. 29483 3 Claims ABSTRACT OF THE DISCLOSURE A safety type lifting hook having a swinging beam pivoted to a frame utilizes a manually controlled latch mechanism to retain or release the beam. When lifting a normal load a safety lock is actuated to prevent accidental unlatching. The improvement resides in the configuration and relationship of the beam latching and locking parts.

This invention relates to load engaging hooks of the type having a fixed portion and a beam portion pivoted to the fixed portion and movable to a closed retaining position.

An object of the invention is to provide an improved latch for engaging the movable beam portion and latching it in load retaining position. By locating the main latch to swing upwardly from a generally horizontal position and providing a suitably shaped cam surface with matching shaped tip on the beam portion the latching operation utilizes a minimum number of parts.

Another object is to provide improved mechanism for locking the latch when a load is being lifted by the hook. A locking element which moves upwardly under load is positioned to directly interfere with the latch structure because of a specially shaped projection on the latch. When in the unloaded or down position the lock element allows release of the latch.

A further object of the invention is to provide simplified robust locking mechanism having a main moving member controlled by a pair of Belleville spring assemblies. A balanced positioning of the Belleville spring devices provides a relatively high locking control load in a compact space.

How the foregoing and other objects and advantages of the invention are accomplished will be evident by reference to the description of the figures in which- FIGURE 1 is a front elevational view of a lifting hook according to this invention showing the parts in closed position before lifting a load.

FIGURE 2 is a side elevational view of the hook shown in FIGURE 1.

FIGURE 3 is a sectional front view showing the hook parts in load carrying position, with certain parts omitted for clarity.

FIGURE 4 is a view similar to FIGURE 3 but showing the parts in load released position.

From the figures it will be seen that the lifting hook assembly includes a frame consisting of a front plate 11 and a rear plate 12 spaced apart by a frame member 13 which extends beyond the plates 11 and 12 to form a handle 14. The spacer frame member 13 is preferably welded or otherwise fastened to the front and rear plates to form an integral frame. At the lower end the spaced plates 11 and 12, a beam member 15 is pivotally supported by a pivot 16 to permit swinging movement of the beam with respect to the frame 10. The frame 10 and the beam member 15 are curved to form an aperture 17 forming the throat of the lifting hook assembly. The beam member 15 is shown in closed position in FIGURES 1 and 3 and in open position in FIGURE 4. At the upper end of the beam 15 when in closed position a latch member 18 is movably supported by a pivot 19 between the frame plates 11 and 12.

The latch member 18 extends beyond the frame plates so that its terminal 20 is accessible for swinging movement inside the periphery of handle 14. A spring 21 urges the latch 18 to its engaged position as shown in FIGURES 1 and 3. A cam portion 22 of the latch 18 is shaped to engage the tip of the beam member 15 to retain it in closed position. Cam surface 22 and the engaging tip portion of beam 15 form complementary surfaces which are substantially the arc of a circle with its center at the center of pivot 19. This configuration produces reliable retention capability for the latch with satisfactory releasing action. A projection or arm 23 attached to the latch member 18 is shaped to cooperate with a locking device in a fashion which will be described below.

The device for locking the latch in closed position when the hook is carrying a load includes a specially shaped control plate member 24 which is supported near the upper end of the frame plates 11 and 12. Control member 24 includes a circular aperture 25 through which the shackle rod or bolt 26 extends. The plates 11 and 12 are provided with apertures 27 and 28 which are elliptical in shape to permit slight vertical motion of the shackle bolt 26. At the lower end of the control plate member 24 there are a pair of abutments 29 and extension legs 30, 30 through which a stop element in the form of a pin 31 projects into guide slots 32 formed in the frame plates 11 and 12. As will be seen in FIGURE 2, the extension in plate 24 includes a channel 33 formed between the legs 30, 30. The projection 23 of the latch member 18 is proportioned so that it fits into the channel 33 between the arms 30, 30.

The shackle bolt 26 transfers the load from frame 10 to the shackle 34 to which may be attached the lifting equipment such as illustrated by link 35 shown in broken outline. When the weight of the load to be lifted is transmitted to the shackle 34, the bolt 26 moves upwardly in the slots 27 and 28 until it reaches the upper end. This movement of the bolt 26 carries the control plate member 24 with it. Movement of the member 24 is resisted by a pair of Belleville springs 36, 36 supported in position around eyebolts 37, 37 which are anchored with respect to the frame plates by the bolts 38, 38. The lower ends of the eyebolts 37, 37 extend through suitable guide apertures 39, 39 in the abutments 29, 29. The Belleville washer assemblies 36, 36 provide the desired amount of restraint so that the automatic locking action takes place when the predetermined amount of lifting action is applied.

A typical lifting sling member in the form of a sling ring 40 and sling tension members 41, 41 is illustrated in FIGURES 1 and 2 in broken outline.

A control rod member 42 is shown connected by a pivot 43 to the end 20 of the latch member 18 and extends through aperture 14a in the handle 14. A loop 44 provides for the attachment of a further control (not shown) which may be used for remote operation of the release mechanism.

To load the lifting hook the beam 15 will be in open position as illustrated in FIGURE 4. The latch and locking parts will be positioned as shown in FIGURE 1. The load supporting ring 40 is placed in position in the throat 17 and the beam 15 is swung into latched position. During the final portion of the swing the tip of the beam member 15 will engage the sloping portion 45 and deflect the latch to permit the beam to swing into position when the latch returns automatically under the influence of spring 21 to the latched position shown in FIGURE 1.

The liftin hook is then in condition to lift the load and as the lifting action increases, the shackle bolt 26 will move upwardly to the upper end of the elliptical openings 27 and 28 in the frame plates. When the load has been increased to the capacity of the springs 36, the full upward travel of the bolt 26 will have occurred and the control member 24 will be in its upper position with the pin 31 also at the upper end of its slot 32. Thus at loads greater than the capacity of springs 36 the pin 31 will be aligned with the end of the latch projection 23. In this position the latch is restrained from movement in the opening direction so that accidental release cannot occur while the load is being carried. In a typical design the capacity of the springs 36 might be, for example, of the normal lifting capacity of the lifting hook. Thus for a hook having a lifting capacity of 20,000 lbs., at loads above 1,000 lbs. the locking mechanism would be effective to prevent accidental unlatching. This percentage can be varied to suit the requirement of any situation, the main objective being that the springs are capable of preventing locking under the influence of tare weight such as the weight of the sling equipment being used to lift the load.

To release the load from the lifting hook it will be deposited at the delivery location and the sling tension reduced until the springs 36 move the stop and the control member downwardly to its lower position as indicated in FIGURE 1. The latch may then be swung about its pivot 19 so that the projection 23 at the latch moves past the stop pin 31 as illustrated in FIGURE 4. When the full swing has been completed the latch cam surface 22 has moved out of contact with the tip of the beam 15 and thus permits it to swing open under the influence of the weight of the sling ring 40. The latch 18 may be moved either by direct manual application of force or by a remotely actuated pull cable which may be connected to the loop 44 of the control rod 42 to permit release of the sling when the hook is in a position not readily accessible to the operator. Alternatively an extension pole can be used for remote release operation.

From the foregoing description, it will be evident that the improved construction for a releasable lifting hook provides a robust and reliable mechanism for latching the releasable beam portion of the lifting hook and further provides a safety locking device having a minimum number of parts thus giving a simple and reliable lock mechanism.

I claim:

1. A hook device including a frame structure having a pair of spaced plates each having a lower curved portion, a load beam pivotally supported between said frame plates and having a curved shape to cooperate with the curved portion of said frame to form a load attachment throat, a load transfer bolt at the upper portion of said frame structure, a latch member pivoted at one end to said frame structure and lying in a transverse direction when in latched position, said latch member having a cam portion engageable with the end of said load beam, a spring element reacting against said latch member urging it to engaged position, the upper portion of said frame structure incorporating vertical lost motion apertures to accommodate said load transfer bolt, a lock control member supported on said bolt for movement therewith, a stop element carried by said control member, said latch member having a projecting arm at its mid portion, said arm having a terminal shape which engages said stop element when it is moved to its upward position, said projecting arm being further shaped to allow it to pass above said stop element when it is moved to its lower position.

2. The device of claim 1 in which said lock control member has a pair of abutments, each abutment having a Belleville spring assembly reacting against it to urge said control member in a downwardly direction with respect to said frame structure.

3. A load engaging hook including a frame structure having the lower portion shaped to engage a connected load member, a complementary load engaging beam part pivotally attached to the lower end of said frame structure, a latch member having a pivotal support in said frame structure and also having a cam portion for engaging the end of said load engaging part when both said load part and said latch member are in load engaged position, a load transfer member located at the upper portion of said frame structure, a cylindrical bolt member connecting said load transfer member to said frame structure, a lost motion aperture in said frame structure through which said cylindrical bolt member extends, a movable element supported in said frame structure by said bolt member, a spring device urging said element downwardly, a stop pin supported in said element and movable with it to the extent of movement permitted by said lost motion aperture, said latch member having a projecting portion shaped to swing past said stop pin when said movable element is in its downward unloaded position and to engage said stop pin when said movable element is in its upward loaded position thereby preventing movement of the latch member away from its engaged position.

9/1938 Lawton. 3/1965 Harley.

ANDRES H. NIELSEN, Primary Examiner 

